Room Acoustics Calculator
Reverberation time, RT60, is the single most important number describing how a room sounds: it is the seconds for sound to fade by 60 decibels after the source stops. The Sabine equation predicts it from the room's volume and its total sound absorption. Enter the room's dimensions and the total absorption in sabins (from your material test data), and this calculator returns the room volume, the RT60, and a rough air-volume-per-sabin figure. Absorption is a user input because coefficients depend on your specific materials and must come from lab reports, not from a hardcoded guess.
Sabine reverberation formula
Volume = length * width * height (cubic feet)
RT60 = 0.049 * volume / total absorption (sabins)
Volume per sabin = volume / total absorption
RT60 (ms) = RT60 * 1,000
The constant 0.049 applies when volume is in cubic feet and absorption is in sabins. RT60 rises with room volume and falls as you add absorption. Doubling the absorption halves the reverberation time.
Acoustic design notes
- Total absorption is the sum of each surface area times its absorption coefficient (in sabins).
- Absorption coefficients depend on material and frequency; use manufacturer lab test reports.
- The Sabine equation assumes a diffuse sound field and is most accurate at moderate reverberation.
- For very dead rooms with high absorption, the Eyring equation is more accurate.
- Speech-clarity rooms typically target under 0.8 seconds; critical-listening spaces aim lower.
Room acoustics: frequently asked questions
What is reverberation time RT60?
RT60 is the time in seconds for a sound to decay by 60 decibels after the source stops. It is the standard measure of how live or dead a room sounds. The Sabine equation estimates it from the room volume and the total sound absorption present.
What is the Sabine equation?
The Sabine equation, in US customary units, is RT60 = 0.049 times volume in cubic feet divided by total absorption in sabins. In metric units the constant is 0.161 with volume in cubic meters. This calculator uses cubic feet and the 0.049 constant.
What is a sabin?
A sabin is the unit of sound absorption. One square foot of a perfect absorber equals one sabin. Total absorption is the sum over every surface of its area times its absorption coefficient. You enter the total absorption directly, since coefficients depend on your specific materials.
Why must I enter absorption myself?
Absorption coefficients vary by material, frequency, and manufacturer, and authoritative values come from lab test reports specific to each product. Rather than hardcode a coefficient, this calculator takes your measured or specified total absorption in sabins so the answer reflects your real room.
What RT60 is good for a room?
It depends on use. Recording studios and home theaters aim for short reverberation, often 0.3 to 0.5 seconds. Speech rooms favor under about 0.8 seconds for clarity; concert halls are deliberately longer. Compare your computed RT60 against the published target for your room type.
Official sources
- National Institute of Standards and Technology: acoustical measurement standards.
- U.S. Access Board: classroom acoustics guidance.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.